linux-kernel - [PATCH v4 10/13] phy: usb: PHY's MDIO registers not accessible without device installed

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Date:   Fri,  3 Jan 2020 13:18:08 -0500
From:   Al Cooper <alcooperx@...il.com>
To:     linux-kernel@...r.kernel.org
Cc:     Al Cooper <alcooperx@...il.com>,
        Kishon Vijay Abraham I <kishon@...com>,
        Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Florian Fainelli <f.fainelli@...il.com>,
        bcm-kernel-feedback-list@...adcom.com (maintainer:BROADCOM BCM7XXX ARM
        ARCHITECTURE), Srinath Mannam <srinath.mannam@...adcom.com>,
        devicetree@...r.kernel.org (open list:OPEN FIRMWARE AND FLATTENED
        DEVICE TREE BINDINGS),
        linux-arm-kernel@...ts.infradead.org (moderated list:BROADCOM BCM7XXX
        ARM ARCHITECTURE)
Subject: [PATCH v4 10/13] phy: usb: PHY's MDIO registers not accessible without device installed

When there is no device connected and FSM is enabled, the XHCI puts
the PHY into suspend mode.  When the PHY is put into suspend mode
the USB LDO powers down the PHY. This causes the MDIO to be
inaccessible and its registers reset to default. The fix is to
disable FSM.

Signed-off-by: Al Cooper <alcooperx@...il.com>
---
 drivers/phy/broadcom/phy-brcm-usb-init-synopsys.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/phy/broadcom/phy-brcm-usb-init-synopsys.c b/drivers/phy/broadcom/phy-brcm-usb-init-synopsys.c
index ee49cbdb55bb..ce4226ac552e 100644
--- a/drivers/phy/broadcom/phy-brcm-usb-init-synopsys.c
+++ b/drivers/phy/broadcom/phy-brcm-usb-init-synopsys.c
@@ -56,6 +56,7 @@
 #define USB_PHY_PLL_LDO_CTL		0x08
 #define   USB_PHY_PLL_LDO_CTL_AFE_CORERDY_MASK		0x00000004
 #define USB_PHY_UTMI_CTL_1		0x04
+#define   USB_PHY_UTMI_CTL_1_POWER_UP_FSM_EN_MASK	0x00000800
 #define   USB_PHY_UTMI_CTL_1_PHY_MODE_MASK		0x0000000c
 #define   USB_PHY_UTMI_CTL_1_PHY_MODE_SHIFT		2
 #define USB_PHY_STATUS			0x20
@@ -229,6 +230,14 @@ static void usb_init_common_7211b0(struct brcm_usb_init_params *params)
 
 	usb_init_common(params);
 
+	/*
+	 * Disable FSM, otherwise the PHY will auto suspend when no
+	 * device is connected and will be reset on resume.
+	 */
+	reg = brcm_usb_readl(usb_phy + USB_PHY_UTMI_CTL_1);
+	reg &= ~USB_PHY_UTMI_CTL_1_POWER_UP_FSM_EN_MASK;
+	brcm_usb_writel(reg, usb_phy + USB_PHY_UTMI_CTL_1);
+
 	usb2_eye_fix_7211b0(params);
 }
 
-- 
2.17.1